Effect of Level and Duration of High Temperatures on Rest in the Peach

Abstract

Rooted ‘Redhaven’ peach [ Prunus persica (L.) Batsch] cuttings were exposed to diurnal temperature cycles. A severe reduction in lateral vegetative bud break was found in plants refrigerated at 4°C and given 8 hr daily exposure to 19° (±0.1°). Nearly complete chilling negation occurred in plants exposed to diurnal cycles including 8 hr of 20° or 21°. Also, effect decreased with increased time (0 to 8 hr per day) of exposure to 24°. Buds on plants exposed to cycles including 20° for 2 and 4 hr showed no chilling negation, but gradual increases in chilling negation occurred with longer exposures to 20°. ‘Harvester’ peach plants were exposed to 2, 7, or 12 days of 23° following the accumulation of one-fourth, one-half, or three-fourths of the chilling requirement. Chilling negation occurred only with the 12-day exposure to 23° when high temperatures were applied following the accumulation of one-fourth and one-half of the chilling requirement. No chilling negation was found after 12 days’ exposure to 23° if three-fourths of the chilling requirement had accumulated before exposure.